Sure. // Libenter.1. The Latin noun "mens, mentis" is feminine.2. "Affecti est" is wrong, because the subject [of your English sentence] is nom. sing. while the participle ["affecti"] as written [by you] is either plural nominative or a singular genitive.

Ah, nunc sequor. Non itellexi hanc partem "ut scriptum". Can I use "sequor" in this context? Also would you interpret the last sentence as "I did not understand" or "I have not understood" (because I mean the former)?

Would "tibi infirmus mentis affectus est" or "infirmi mentis affectus est" also make sense, seeing as one meaning of the noun "affectus affectus (4th)" in whitakers words is "state (of body/mind)"? If not, do you know why?

Also, do you have any tips when using the subjunctive, because whenever I use it, I'm never sure whether it will be interpreted as intended (except in certain structures like ut clauses)?

Are there any good ways to ask if something makes sense? I can't find any way to ask if something is ok, or alright, or makes sense.